Encoding error when converting UploadedFile to json with binary tempfile

[maltoe]

Hey,

we have an issue with ActionDispatch::Http::UploadedFile and to_json. We're using the Gelf gem for logging to a Graylog2 instance. After (successful) API calls to a file upload action, Gelf errors in to_json. We traced the problem down to an instance of UploadedFile in Gelf's parameters hash which it tries to convert to JSON to send to the server.

The UploadedFile contains a Tempfile in binary mode which seems to be included in the JSON representation, including its content. The content from read is supposed to be encoded in ASCII-8BIT, yet contains binary data.

Not really sure where the best place to fix this behaviour is (Ruby's Tempfile, Active Support's JSON, or here), but I thought UploadedFile for sure should not include the file's content in the JSON representation. Imho.

Steps to reproduce

Anyway, here's a test case:

https://gist.github.com/maltoe/a1b9bfc83be1c0eaef208ade9cbdfdad

Expected behavior

Not really sure, either catch these conversion errors in JSON (i.e. not convert the string to UTF-8, or do character replacement in there), or simply not include the tempfile's content in the json.

Actual behavior

BugTest#test_to_json_with_non_ascii_data:
Encoding::UndefinedConversionError: "\x80" from ASCII-8BIT to UTF-8

Possible fix (our current monkey-patch)

class UploadedFile
  def to_hash
    instance_values.except 'tempfile'
  end
end

System configuration

Rails version:
We use 4.2.5.2, but I tested on master.

Ruby version:
2.2.4

[maclover7]

Hmm, I'm not sure if converting uploaded files to JSON is something that we want to support. Feel free to open a PR, and then we can continue the discussion there. :)

[sgrif]

This isn't supported usage.